The Little House on the Prairie series, with its tales of earnest, rosy-cheeked lasses in pinafores, has been a literary staple of young girls for generations.

Published in the 1930s and 1940s and written by Laura Ingalls Wilder, the books tell the true story of childhood on the American frontier — making maple syrup, birthing calves, weathering the scourge of disease.

One particularly memorable segment recounts the terrible disease that claimed the eyesight of the author’s 14-year-old sister, Mary Ingalls, in 1879. In the accounts, the devastating disease was scarlet fever.

Or was it?

For a physician and a Little House fan, the question turned into a years-long research project that they describe in a paper published in the journal Pediatrics.

Dr. Beth Tarini, an assistant professor of pediatrics in the Child Health Evaluation and Research Unit at the University of Michigan’s C.S. Mott Children’s Hospital, had been wondering whether scarlet fever could cause blindness ever since 2000, when she was a medical student.

One day, the students were discussing scarlet fever, a strep-throat-related diagnosis that’s much less common today than the flu but more common than meningitis. A sore throat and a red-spotted rash that feels like sandpaper are its hallmarks.

The attending physician didn’t think so, but Tarini wasn’t persuaded. “I was like, Well, then, how can we explain that Mary Ingalls went blind from scarlet fever?”

Tarini started poking around in medical texts from the late 1800s, when the events in Little House took place, to see if scarlet fever was linked with blindness. There were some reports, but the connection was far from obvious. Then Tarini checked Pioneer Girl, Wilder’s memoirs that served as inspiration for her Little House series. There’s mention of a headache and fever but no rash — and there’s reference to a stroke that left one side of Mary’s face drooping. Tarini thought that sounded more like a case of temporary paralysis than a stroke. With no mention in the memoirs of either of scarlet fever’s distinguishing symptoms — a sore throat or a rash — preceding Mary’s blindness, Tarini was perplexed.

What could have caused Mary’s blindness? The possibilities were too overwhelming, from infectious diseases to biological conditions to genetic mutations that physicians at the time could never have considered. So Tarini set aside her research for 10 years. It collected dust in the corner of her office until she unearthed it recently.

Tarini’s graduate student, Sarah Allexan — now a medical student at the University of Colorado — shouldered the challenge of solving the mystery. Allexan rifled through newspapers from the time of Mary’s illness and sifted through the registry at the Iowa School for the Blind that she’d attended. The school’s documents said that Mary had suffered “brain fever,” a common term for encephalitis or meningitis in that era.

With multiple sources casting doubt on the scarlet fever diagnosis, Tarini concluded that the association was simply wrong: perhaps Wilder was misinformed or maybe she’d been pressured by her editor to blame scarlet fever since it was one of the best-known causes of childhood death during that time.

It’s even possible that Wilder was influenced by another classic, Little Women, which was written in the 1860s. In that tome, Beth, one of the sisters, succumbs to scarlet fever.

“It was a very deadly disease of childhood,” says Tarini. “People probably thought if it could kill you, it could make you go blind.”

Ultimately, Tarini decided that either meningitis or encephalitis were the culprits. Not only were they alluded to by the School of the Blind, but they both can result in fever and headache, and they both can inflame facial nerves, which could potentially cause gradual blindness.

Was this literary-cum-medical excavation an important undertaking or an indulgent exercise? Tarini’s colleagues were mixed. But she believes getting to the bottom of why Mary lost her sight offers a valuable clinical lesson about hype versus reality. “When I tell a parent their child has scarlet fever, there is dead silence in the room and the parent gets a little wide-eyed,” she says. “They say, Scarlet fever can kill you.”

That’s technically true, but in reality it’s less likely with currently available medical care and antibiotics. Still, modern-day parents continue to associate scarlet fever with a deadly illness when it’s actually just a sore throat with a rash.

The study also highlights the fact that diagnoses don’t occur in vacuums, and that providing patients with the context to understand the diagnosis is just as critical as the medical pronouncement itself. “As physicians, we should realize that the patients we treat have perceptions of disease that are informed by their life experiences,” says Tarini. “The diagnoses I give can have power beyond what I see because of the patient’s lived experiences.” And those include accounts from a beloved childhood series.